Re: manually creating indices to speed up indexing with app-knowledge

Otis Gospodnetic wrote:

Britske,

The place to ask is on java-user@lucene if you want to go low-level.  Look at IndexWriter and even DocumentsWriter classes.

I'm not sure how up to date it is, but look at http://lucene.apache.org/java/2_9_0/fileformats.html

You should also try streaming your data directly into Solr, it's the fastest way to index.  Info on the Wiki.

Otis
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----- Original Message ----
> From: Britske <gbrits@gmail.com>
> To: solr-user@lucene.apache.org
> Sent: Mon, November 2, 2009 4:40:04 PM
> Subject: manually creating indices to speed up indexing with app-knowledge
>
>
> This may seem like a strange question, but here it goes anyway.
>
> Im considering the possibility of low-level constructing indices for about
> 20.000 indexed fields (type sInt) if at all possible . (With indices in this
> context I mean the inverted indices from term to Documentid just to be 100%
> complete)  
> These indices have to be recreated each night, along with the normal
> reindex.
>
> Globally it should go something like this (each night) :
> - documents (consisting of about 20 stored fields and about 10 stored &
> indexed fields) are indexed through the normal 'code-path' (solrJ in my
> case)
> - After all docs are persisted (max 200.000) I want to extract the mapping
> from 'lucene docid' --> 'stored/indexed product key'
> I believe this should work, because after all docs are persisted the
> internal docids aren't altered, so the relationship between 'lucene docid'
> --> 'stored/indexed product key' is invariant from that point forward.
> (please correct if wrong)
> - construct the 20.000 inverted indices on such a low enough level that I do
> not have to go through IndexWriter if possible, so  I do not need to
> construct Documents, I only need to construct the native format of the
> indices themselves. Ideally this should work on multiple servers so that the
> indices can be created in parallel and the index-files later simply copied
> to the index-directory of the master.
>
> Basically what it boils down to is that indexing time (a reindex should be
> done each night)  is a big show-stopper at the moment, although we've tried
> and tested all the more standard optimization tricks & techniques, as well
> as having build a  home-grown shard-like indexing strategy which uses 20
> pretty big servers in parallel. The 20.000 indexed fields are still simply
> killing.
>
> At the same time the app has a lot of knowledge of the 20.000 indices.
> - All indices consist of prices (ints) between 0 and 10.000
> - and most important: as part of the document construction process the
> ordening of each of the 20.000 indices is known for all documents that are
> processed by the document-construction server in question. (This part is
> needed, and is already performing at light speed)
>
> for sake of argument say we have 5 document-construction servers. Each
> server processes 40.000 documents. Each server has 20.000 ordered indices in
> its own format readily available for the 40.000 documents it's processing.
> Something like: LinkedHashMap> -->
>
>
> Say we have 20 indexing servers. Each server has to calculate 1.000 indices
> (totalling the 20.000)
> We have the 5 doc-construction servers distribute the ordered sub-indices to
> the correct servers.
> Each server constructs an index from 5 ordered sub-indices coming from 5
> different construction-servers. This can be done efficiently using a
> mergesort (since the sub-indices are already sorted)
>
> All that is missing (oversimplifying here ) is going from the ordered
> indices in application-format to the index-format of lucene (substituting
> the productids by the lucene docid's along the way) and stream it to disk.
> I believe this would quite posisbly give a really big indexing improvement.  
>
> Is my thinking correct in the steps involved?
> Do you believe that this indeed would give a big speedup for this specific
> situation  
> Where would I hook in the SOlr / lucene code to construct the native format?
>
>
> Thanks in advance (and for making it to here)
>
> Geert-Jan
>
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